The invention relates to a rib element for use in support structures for wings, guide surfaces, and stabilizers of aircraft, the rib element being manufactured from a composite material and comprising flanges inter-connected with one another at rounded corners. The invention further relates to a composite flange for use in structures of aircraft, the composite flange comprising at least two interconnected flanges and a rounded corner between the flanges. The field of the invention is described in closer detail in the preambles of the independent claims.
A wing of aircraft, such as aeroplanes and the like, comprises skin plates, between which the actual support structure of the wing resides, the support structure typically comprising a front spar and a rear spar in the longitudinal direction of the wing and wing ribs provided in the transverse direction of the wing to connect the front and rear spars. Further, a plurality of stringers is usually provided between the wing ribs and the skin plates. The structure of stabilizers as well as of guide surfaces, such as spoilers, flaps, rudders, etc., is typically similar to that of a wing and comprises rib elements comparable with wing ribs.
In modern aircraft, more and more structural parts manufactured from a composite material are used instead of conventional components manufactured from metal parts that have been riveted together. The use of composite materials enables the weight of the structures to be reduced. It is also possible to manufacture various flange structures from a composite material wherein two or more flanges constitute an angle with respect to one another. A composite material is known to be stiff yet fragile, so to be on the safe side, every effort is made to dimension a corner of a flange structure such that it is extremely stiff. Consequently, the flanges are made quite thick, which results in a heavy flange structure. A known way to try and reduce the weight of a flange structure is to make the thickness of the flanges to be reduced over a distance starting from the corner, leaving the corner with a sufficient thickness of material. General design rules for composite structures, however, determine that a change in thickness should not take place discontinuously but a reduction in thickness is to take place gradually. Generally, the change in thickness/length ratio should be 1/20. This means that, while taking the design rules into account, the relatively large thickness of the flanges required by the corner cannot be reduced sufficiently in order to make the structure lighter. The problem is thus that the current solutions do not enable a sufficiently strong and yet light flange structure to be produced, although such features are extremely important properties for aircraft components.